The present invention relates to a series of new 7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylic acid derivatives, to their use as antibiotics and to their preparation.
The compounds of the invention possess the following basic structure, in which the numbering shown is that used hereinafter to define the compounds: ##STR5##
It will be seen that this structure is similar to the structure of certain penicillin derivatives, specifically the 2-penem derivatives, which possess the following basic structure: ##STR6## except that the sulphur atom of the 2-penem compounds has been replaced by a carbon atom and, indeed, the compounds of the invention could be called "1-carba-2-penem-3-carboxylic acid derivatives" (using the 2-penem numbering system).
A natural antibiotic having the 7-oxo-1-azabicyclo[3.2.0]hept-2-ene structure has been isolated and has been found to have extraordinarily potent antibacterial activity, as described in Japanese Patent Application Kokai (i.e. as laid-open to public inspection) No. 73191/76. This natural antibiotic is called "thienamycin" and has been found to be (5R,6S)-3-(2-aminoethylthio)-6-[1-(R)-hydroxyethyl]-7-oxo-1-azabicyclo[3.2 .0]hept-2-ene-2-carboxylic acid, i.e.: ##STR7##
However, compounds of the thienamycin type have been found to be unstable, as described in The Journal of Antibiotics, 32, 1 (1979) and it would, therefore, be desirable to discover compounds which, whilst retaining the antibiotic activity of thienamycin, have greater chemical stability.